The present invention relates to an automatic braking control system with object detection system interaction, and particularly to techniques for automatic braking control according to which a braking system is activated automatically without any driver""s braking action when a host vehicle is closing on a frontally-located obstacle or a vehicle ahead.
In recent years, there have been proposed and developed various braking control systems that determine a possibility of collisions based on both a relative distance between a host vehicle and an object, such as an obstacle in front and a preceding vehicle running ahead of the host vehicle, and a relative velocity of the host vehicle to the preceding vehicle, for the purpose of automatic activation of a braking system, collision avoidance, slippage control of steered wheels, or the like. Japanese Patent Provisional Publication No. 5-242396 has disclosed an active safety system which determines that the possibility of a collision is low when a relative velocity to the preceding vehicle is below a predetermined threshold value and an acceleration value of a host vehicle is above a predetermined acceleration value, and thus prevents a braking system from being undesirably activated automatically when the host vehicle is passing the preceding vehicle. Japanese Patent Provisional Publication No. 5-58257 has disclosed a steered-wheel slippage control system which reduces a braking force or sets the braking force to zero in order to prevent undesirable slippage of steered road wheels when the road wheels are steered during an automatic braking mode. Japanese Patent Provisional Publication No. 2001-233189 has disclosed an automatic preview braking control system capable of generating a minute braking pressure (that is, pre-application of the brakes) based on a vehicle running state when an anti-skid braking system (ABS) electronic control unit (ECU) determines that the preliminary braking pressure application is required as a preview. Assuming that the possibility of a collision is merely determined based on both a relative velocity of a host vehicle to a preceding vehicle and an acceleration rate of the host vehicle, there is a possibility that the operating mode of the braking system cannot be shifted to an automatic braking mode under a particular condition where the host vehicle is approaching the preceding vehicle due to driver""s inattentive driving during which the relative velocity is below the predetermined threshold value and the time rate of change in the host-vehicle speed exceeds the predetermined acceleration value. On the other hand, in the system that the braking force is reduced depending on whether road wheels are steered, there is an increased tendency for a shift to the automatic braking mode to be inhibited even during cornering wherein the automatic braking is required.
Accordingly, it is an object of the invention to provide an automatic braking control system with object detection system interaction, which avoids the aforementioned disadvantages.
It is another object of the invention to provide an automatic braking control system with object detection system interaction, which is capable of precisely determining the presence or absence of a driver""s intention for obstacle-avoidance or a driver""s intention to pass the preceding vehicle, in other words, the presence or absence of a driver""s intention for lane-changing, so as to optimally control a shift to an automatic braking mode and to prevent an undesirable shift to the automatic baking mode.
In order to accomplish the aforementioned and other objects of the present invention, a braking control system with object detection system interaction comprises a relative-distance detector that detects a relative distance of a frontally positioned object relative to a host vehicle, a vehicle speed sensor that detects a host vehicle speed of the host vehicle, an automatic braking control unit configured to be electronically connected to at least the relative-distance detector and the vehicle speed sensor for automatically controlling, depending on both the relative distance and the host vehicle speed, a braking force needed for an automatic braking operation without driver""s braking action when the host vehicle is approaching the frontally positioned object, the automatic braking control unit comprising a detection section that detects the presence or absence of a driver""s intention for lane-changing, the automatic braking control unit limiting the automatic braking operation in the presence of the driver""s intention for lane-changing.
According to another aspect of the invention, a braking control system with object detection system interaction comprises an object detection means for detecting a relative distance of a frontally positioned object relative to a host vehicle, a vehicle speed detection means for detecting a host vehicle speed of the host vehicle, an automatic braking control means configured to be electronically connected to at least the object detection means and the vehicle speed detection means for automatically controlling, depending on both the relative distance and the host vehicle speed, a braking force needed for an automatic braking operation without driver""s braking action when the host vehicle is approaching the frontally positioned object, the automatic braking control means comprising means for detecting the presence or absence of a driver""s intention for lane-changing, the automatic braking control means limiting the automatic braking operation in the presence of the driver""s intention for lane-changing.
According to a further aspect of the invention, an automatic preliminary braking control system with object detection system interaction comprises a relative-distance detector that detects a relative distance of a frontally positioned object relative to a host vehicle, a vehicle speed sensor that detects a host vehicle speed of the host vehicle, a brake switch whose signal indicates if a brake pedal is depressed, an accelerator stroke sensor that-detects an accelerator opening, an automatic braking control unit configured to be electronically connected to at least the relative-distance detector, the vehicle speed sensor, the brake switch and the accelerator stroke sensor for automatically controlling, depending on the relative distance, the host vehicle speed, the signal from the brake switch and the accelerator opening, a braking force needed for preliminary braking control initiated prior to driver""s braking action when the host vehicle is approaching the frontally positioned object, the automatic braking control unit comprising a target deceleration rate calculation section that calculates a target deceleration rate, needed to avoid the host vehicle from being brought into collision-contact with the frontally positioned object, from an expression Gx*={Vm2xe2x88x92(Vmxe2x88x92dL/dt)2}/2L, where Gx* is the target deceleration rate, Vm is the host vehicle speed, L is the relative distance, and dL/dt is a time rate of change of the relative distance, a comparison section that determines whether the target deceleration rate is greater than or equal to a predetermined deceleration-rate threshold value, and a detection section that detects the presence or absence of a driver""s intention for lane-changing, the automatic braking control unit inhibiting the preliminary braking control, when either of a condition that the brake pedal is undepressed, a condition that the accelerator opening is less than or equal to a predetermined threshold value substantially corresponding to a closed position of an accelerator, a condition that the target deceleration rate is greater than or equal to the predetermined deceleration-rate threshold value, and a condition that the driver""s intention for lane-changing is absent, is unsatisfied.
According to a still further aspect of the invention, an automatic supplementary braking control system with object detection system interaction comprises a relative-distance detector that detects a relative distance of a frontally positioned object relative to a host vehicle, a vehicle speed sensor that detects a host vehicle speed of the host vehicle, a pressure sensor that detects an actual braking pressure, an automatic braking control unit configured to be electronically connected to at least the relative-distance detector, the vehicle speed sensor and the pressure sensor for automatically controlling, depending on the relative distance, the host vehicle speed and the actual braking pressure, a braking force needed for supplementary braking control through which a value of a controlled quantity is brought closer to a target deceleration rate needed for collision-avoidance when the host vehicle is approaching the frontally positioned object, the automatic braking control unit comprising a target deceleration rate calculation section that calculates the target deceleration rate, needed to avoid the host vehicle from being brought into collision-contact with the frontally positioned object, from an expression Gx*={Vm2xe2x88x92(Vmxe2x88x92dL/dt)2}/2L, where Gx* is the target deceleration rate, Vm is the host vehicle speed, L is the relative distance, and dL/dt is a time rate of change of the relative distance, a computation section that computes a target braking pressure based on the target deceleration rate, a comparison section that determines whether the actual braking pressure is less than the target braking pressure, and a detection section that detects the presence or absence of a driver""s intention for lane-changing, the automatic braking control unit decreasingly compensating for the target braking pressure for limiting the supplementary braking control, when a condition that the actual braking pressure is less than the target braking pressure and a condition that the driver""s intention for lane-changing is present, are both satisfied.
According to another aspect of the invention, a method for automatically controlling a braking force needed for an automatic braking operation without driver""s braking action when a host vehicle is approaching a frontally positioned object, the method comprises detecting a host vehicle speed, detecting a relative distance of the frontally positioned object relative to the host vehicle, detecting a signal from a brake switch, detecting an accelerator opening, detecting an actual braking pressure, calculating a time rate of change of the relative distance, calculating a target deceleration rate based on the host vehicle speed, the relative distance, and the rate of change of the relative distance, computing a target braking pressure based on the target deceleration rate, detecting the presence or absence of a driver""s intention for. lane-changing, inhibiting preliminary braking control initiated prior to driver""s braking action, when either of a condition that the brake pedal is undepressed, a condition that the accelerator opening is less than or equal to a predetermined threshold value substantially corresponding to a closed position of an accelerator, a condition that the target deceleration rate is greater than or equal to a predetermined deceleration-rate threshold value, and a condition that the driver""s intention for lane-changing is absent, is unsatisfied, and decreasingly compensating for the target braking pressure for limiting supplementary braking control, when a condition that the actual braking pressure is less than the target braking pressure and a condition that the driver""s intention for lane-changing is present, are both satisfied.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.